1. Field of the Invention
The invention relates to double valve assemblies used for safety purposes in connection with industrial equipment such as presses, and more particularly, to means for indicating discrepant positions between the two valves of the double valve assembly. Double valve assemblies of this type are disclosed in Di Tirro et al. U.S. Pat. No. 2,906,246, Mahorney et al. U.S. Pat. No. Re. 28,520, Sweet U.S. Pat. No. 3,757,818 and Cameron U.S. Pat. No. 3,858,606. They are of two general types. In the first type, two three-way valves are so arranged that both inlet and exhaust flows to and from the working port are in parallel through the two valves. The second type is so arranged that the inlet flow is in series through the two valves but the exhaust flow is in parallel. In both cases the valves are piston operated and controlled by solenoid-operated pilot valves.